If you join the vintagejapanesesewingmachine group on Yahoo, you might get some answers to your questions. I don't know any of the answers to your questions. I suspect no one else does either. JA-33 is not listed in the list of Japanese manufacturers I've seen. I'm not that knowledgeable about Japanese machines, but I understand there aren't many records available. You pretty much have to go by how it looks and find matching machines to get manuals, etc.
Does it work well?
bkay